Breaking News / Tory Hargro, USA TODAY

by Doug Stanglin, Michael Winter and Neha Ramani, USA TODAY

by Doug Stanglin, Michael Winter and Neha Ramani, USA TODAY

WEST LAFAYETTE, Ind. -- A 23-year-old teaching assistant walked into a basement classroom at Purdue University on Tuesday and shot dead a fellow TA before calmly walking outside and surrendering to a police officer.

Cody M. Cousins, of Warsaw, Ind., was booked on a preliminary charge of murder in the killing of 21-year-old Andrew Boldt, a senior in electrical engineering from West Bend, Wis. Cousins is being held without bail in the Tippecanoe County jail.

Cousins was an undergraduate teaching assistant in computer engineering, and Boldt assisted an electrical engineering class. Both courses are taught by David G. Meyer, a professor of electrical and computer engineering, the Lafayette Journal & Courier reported.

Purdue Police Chief John Cox said at an evening news briefing that Cousins was also connected to an address in Centerville, Ohio.

Cox said the suspect appeared to have targeted Boldt in the classroom of the Electrical Engineering Building about noon and didn't attack anyone else. Witnesses reported hearing four or five shots.

The motive and the relationship between the students remained unknown.

"The individual entered the facility and took the actions that he took, and then immediately left the facility without any other interaction that we're aware of," Cox told reporters earlier.

The suspect walked outside -- unarmed -- and turned himself in to a West Lafayette police officer.

Cox said the suspect did not resist arrest but was not otherwise cooperating with police.

West Lafayette Police Chief Jason Dombkowski said Cousins had had "prior contact" with police. Records show he was arrested in January 2012 on suspicion of public intoxication, the Journal & Courier said.

The initial campus-wide lockdown was partially lifted after about two hours, although police continued to search the engineering building.

"The campus is safe, it has been cleared," Purdue Provost Timothy Sands said at an afternoon update. "We're encouraging students to continue about their usual business on the rest of the campus except for the Electrical Engineering Building."

Sands announced at the evening news conference that classes were canceled the rest of the day and Wednesday.

In June he will become president of Virginia Tech, site of the April 2007 massacre that left 32 people and the student gunman dead.

University President Mitch Daniels was traveling in Colombia but cut short the trip and is returning to Indiana.

A candlelight vigil was scheduled for 8 p.m. on campus.

Ben Snyder, a senior from Fort Wayne, Ind., told the Journal & Courier that he heard two shots followed by shouts of "get down, get down!" Snyder also said he saw at least one person being taken away in handcuffs by police and "a guy with blood on his hands."

The newspaper said one male was brought outside the Electrical Engineering Building with his hands behind his back.

Erica Ambrose, a senior in the School of Agriculture, was attending class in the building when the shooting occurred.

"We heard shouting downstairs and it sounded like people were running through the hallways, just yelling at each other," she toldThe Exponent, the student newspaper.

Cousins worked there as a reporter in 2011, the paper reported hours later.